Adhesive film dressings for medical applications are well-known in the art. Transparent film dressings comprising a polyurethane film coated on one side with a medical grade, pressure-sensitive adhesive are presently used for applications such as IV catheter tapes, dermal ulcer dressings, surgical incision dressings and as occlusive covers for burns and skin donor sites. One such polyurethane film dressing is available from Johnson & Johnson, New Brunswick, N.J., under the trade name Bioclusive.RTM. Transparent Dressing. Such polyurethane dressings are transparent, elastomeric and moisture vapor permeable while impervious to liquids and bacteria.
Typical elastomeric film dressings for medical applications are described in U.S. Pat. Nos. 4,413,621 and 4,614,183. As disclosed in these references, the polymeric films may be prepared from polyurethanes such as Goodrich Estane.RTM. polyurethane and from elastomeric polyesters such as DuPont Hytrel.RTM. copolyester ether elastomer, or from blends of such polyurethanes and polyesters. The films may have a thickness of from about 0.5 to 10.0 mils and are preferably from about 1 to 3 mils thick. The films preferably have a moisture vapor transmission rate of at least 100, and most preferably from about 200 to 1200 grams water per square meter per 24 hrs. (g/M.sup.2 /day) as determined by ASTM test E96 at 100.degree. F. and 90.degree. relative humidity.
The films are coated with a medical grade pressure-sensitive adhesive acceptable for long-term skin contact such as those disclosed in U.S. Pat. Nos. 3,189,581; 3,218,357; 3,325,459 and 4,112,213. These adhesives are generally copolymers of 2-ethylhexyl acrylate and vinyl acetate in ratios of approximately 60 to 70 parts of the acrylate and 30 to 40 parts of the vinyl acetate. The polymers may also contain small amounts of N-tertiary butylacrylamide as a third monomer and a cross-linking agent. A preferred adhesive is a copolymer of approximately 70% 2-ethylhexyl acrylate and 30% vinyl acetate containing from 0.01 to 1% of a silane cross-linking agent as disclosed in U.S. Pat. No. 4,112,213. Water-based adhesives and hot melt adhesives may also be employed. The adhesive is deposited on the film by solvent spreading, transfer coating, extrusion or other known method.
Polyurethane film dressings of the prior art were evaluated for use as protective coverings over friction blisters and skin areas where friction blisters were likely to develop. Although these films provided effective protection while they remained in place, problems were experienced in retaining the film on the skin surface due to the rubbing action inherent in such applications. While one possible solution was to use a more aggressive adhesive with a higher level of adhesion, this could prove disadvantageous in certain applications and on certain individuals. A more preferable solution was to utilize the presently available medical grade, pressure-sensitive adhesives and to modify the film to improve performance.
It is accordingly an object of the present invention to provide an improved adhesive film dressing particularly adapted for use as a protective covering over friction blisters or areas of the skin susceptible to the development of friction blisters. It is a further object of this invention to provide an improved adhesive film blister dressing which utilizes conventional medical grade, pressure-sensitive adhesives. These and other objects of the present invention will be apparent from the ensuing description and claims.